Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 012312
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
612 PM EST SUN MAR 1 2015

.AVIATION...

EASTWARD EXPANSION IN MVFR STRATUS WILL COMMENCE THROUGH THE
OVERNIGHT PERIOD AS A LOW/MID LEVEL TROUGH MOVES ACROSS THE REGION.
THIS PROCESS WILL HELP STEEPEN LAPSE RATES...PROVIDING A NOTED
INCREASE IN WEST-SOUTHWEST WINDS WITH GUSTS INTO THE 20 KNOT DURING
THE EARLY-MID MORNING HOURS.  DRIER AIR ARRIVES ON MONDAY UNDER
INCREASING HIGH PRESSURE.  THIS WILL LEAD TO A DECREASE IN CLOUD
COVERAGE BY LATE MORNING AND EARLY AFTERNOON.  WINDS WILL EASE WITH
TIME THROUGH THE DAY.

FOR DTW...BRIEF PAUSE IN LOWER CLOUD /MVFR/ DEVELOPMENT OVER THE
NEXT SEVERAL HOURS...SATELLITE TRENDS SUGGESTING A RETURN TO MVFR
/CIGS 2500 FT/ BY 02-03Z.

//DTW THRESHOLD PROBABILITIES...

* LOW IN CEILINGS BELOW 5000 FT THROUGH MIDNIGHT...HIGH MONDAY
  MORNING.

&&

.PREV DISCUSSION...ISSUED 305 PM EST SUN MAR 1 2015

SHORT TERM...THIS EVENING AND TONIGHT

UPSTREAM RADAR RETURNS SUGGEST THE LIGHT SNOW WHICH HAS IMPACTED
METRO DETROIT/ANN ARBOR AND POINTS SOUTH THIS AFTERNOON WILL
CONTINUE TO DIMINISH IN INTENSITY BEFORE COMING TO A COMPLETE END
BETWEEN 20Z AND 23Z. SOME REINTENSIFICATION AND A NORTHWARD SHIFT IN
THE MID LEVEL FRONTAL DYNAMICS LED TO A BRIEF PERIOD OF MODERATE
SNOW ACROSS LENAWEE AND MONROE COUNTIES...WHERE TOTAL DAYTIME
ACCUMULATIONS LIKELY RANGED FROM 1 TO 2 INCHES. THE DYNAMIC FORCING
FOR THIS SNOW OCCURRED WITHIN THE EXIT REGION OF A 150KT UPPER JET
STREAK EXTENDING ACROSS FAR SRN LOWER MI THIS AFTERNOON. THE FRONTAL
CIRCULATION WILL SLIDE EAST LATE THIS AFTERNOON AS AN APPROACHING
MID LEVEL WAVE FOCUSES THE UPPER JET SUPPORT FARTHER TO THE EAST.
MID LEVEL DRY AIR ACTUALLY PRECEDES THIS WAVE AND WILL ARRIVE INTO
SE MI THIS EVENING.

THE 19Z SFC ANALYSIS DOES SHOW A TROUGH AXIS OVER WISCONSIN. THIS
FEATURE WILL TRACK INTO LOWER MI TONIGHT WHILE A FAST MOVING SHORT
WAVE TRAVERSES LOWER MI IN THE 06Z TO 09Z TIME FRAME. DESPITE RATHER
GOOD MID LEVEL HEIGHT FALLS AND DIFF CYCLONIC VORT ADVECTION...A
LACK OF MID LEVEL MOISTURE WILL LIMIT SNOW POTENTIAL WITH THIS
SYSTEM. THERE IS HOWEVER SOME LOW LEVEL MOISTURE POOLING ALONG THE
SFC TROUGH OVER WISCONSIN AND LINGERING LAKE MOISTURE OVER WRN AND
CNTL LOWER MI. 850MB TEMPS WILL DROP ALONG THE SFC TROUGH LATE THIS
EVENING AND OVERNIGHT WHICH WILL STEEPEN LOW LEVEL LAPSE RATES. THIS
COMBINED WITH THE LOW LEVEL MOISTURE MAY SUPPORT SOME BRIEF LIGHT
SNOW SHOWERS AND FLURRIES. IN FACT...GOOD SUPERSATURATION WITH
RESPECT TO ICE WITHIN THE CLOUD LAYER ACROSS CNTL LOWER MI HAS BEEN
QUITE EFFICIENT IN GENERATING SOME -SN/FLURRIES THIS
AFTERNOON...CONDITIONS WHICH ARE EXPECTED TO PERSIST THROUGH THE
NIGHT. THE ARRIVAL OF COLDER 850MB TEMPS OVERNIGHT WILL BE
ACCOMPANIED BY AN INCREASE IN THE WESTERLY GRADIENT. WITH A DEEPENING
MIXED LAYER...SOME GUSTINESS IN THE WINDS ARE EXPECTED /LIKELY
PUSHING 25 MPH AT TIMES/. SFC TEMPS MAY NOT DROP INTO THE TEENS
UNTIL VERY LATE IN THE NIGHT DUE TO POTENTIAL WELL MIXED BOUNDARY
LAYER. THE INCREASE IN WINDS WILL HOWEVER DROP WIND CHILL READINGS
INTO THE SINGLE DIGITS OVERNIGHT.

LONG TERM...

MODELS CONTINUE TO DISAGREE ON DYNAMIC INTERACTION BETWEEN TODAY`S
NW TERRITORIES/NUNAVUT TROUGH AND TRAILING LOW AMPLITUDE ARCTIC
ENERGY LEADING TO WIDENING SOLUTION SPACE (BETWEEN EC/GFS/GEM) ALOFT
DESPITE DECREASING LEAD TIME. THE 12Z GFS AND 00Z ECMWF SEEMINGLY
BEGAN TO CONVERGE ON A SOLUTION BEFORE THE 12Z ECMWF TOOK A STEP
BACK TOWARD YESTERDAY`S DEPICTION. THE GFS, MEANWHILE, HAS SEEMINGLY
LEAPFROGGED THE GEM FROM A CONSENSUS STANDPOINT, LEAVING THE LATTER
AS AN OUTLIER AS IT APPEARS TO STRUGGLE WITH OVERALL NORTHERN STREAM
EVOLUTION. A JUMP NORTH FROM THE UKMET AT LEAST OFFERS SOME
CONFIDENCE IN THE SIMILAR ECMWF OF A WEAK LOW OR OPEN SURFACE WAVE
TRANSLATING FROM THE QUAD-CITIES TO THE TRI-CITIES. WITH THAT IN
MIND, A WINDOW OF OPPORTUNITY IS OPENED FOR A MORE AGGRESSIVE
FORECAST ACROSS THE SOUTH IN TERMS OF HIGHER TEMPERATURES AND FASTER
TRANSITION TO WARMER PTYPES.

BY THE TIME IT REACHES LOWER MI, MAIN MODEL DIFFERENCES ARE IN
PLACEMENT/AMPLITUDE BUT ARE GENERALLY SIMILAR DYNAMICALLY WHICH AT
LEAST PROVIDES SOME INSIGHT INTO OVERALL GOVERNING DYNAMICS. PRIMARY
FORCING WILL BE STRONG 290-315K DEEP LAYER ISENTROPIC ASCENT
CENTERED 15-21Z PER 12Z ECMWF. ASCENT WILL BE ACCOMPANIED BY
EXCELLENT MOISTURE TRANSPORT LEADING TO A 6 TO 9 HOUR PERIOD OF H85-
H7 LAYER SPECIFIC HUMIDITY OVER 4 G/KG EVEN ACROSS THE FAR NORTH
WHERE THERMAL PROFILES SUPPORT ALL SNOW. DIFFICULT TO DISSECT TIMING
GIVEN THAT FEATURES ARE STILL OUTSIDE OF THE NAM`S GRID AND CAUSING
ERRATIC SOLUTIONS, BUT THE EVENT HAS THE EARMARKS OF A QUICK-HITTER.
HEAVIEST PRECIPITATION RATES SHOULD CONCENTRATE WITHIN STRONGEST
WARM ADVECTION WHICH IS LARGELY EXPECTED TO OCCUR BEFORE LOWER
LEVELS CAN RISE ABOVE FREEZING. THUS, A QUICK 1-3", LOWER
SOUTH/HIGHER NORTH IS EXPECTED. NOT OUT OF THE QUESTION THAT A
FOCUSED AREA OF HIGHER INTENSITY COULD PRODUCE LOCALLY HIGHER
AMOUNTS SOMEWHERE, BUT THAT WILL BE BETTER ADDRESSED WHEN THE SYSTEM
IS WITHIN 48 HOURS.

H7-H5 DRY SLOT, AIDED BY THE STRONG MID-LEVEL WIND FIELD, WILL THEN
WRAP BENEATH THE JET MAX AND MAKE A STRONG PUSH ABOVE THE CWA AFTER
18Z, CALLING INTO QUESTION THE DURATION AND INTENSITY OF ANY PRECIP
THAT FILLS IN BEHIND THE LEAD EDGE (E.G. NON-SNOW PRECIP). TOO EARLY
TO MAKE ANY SIGNIFICANT CHANGES, BUT CONFIDENCE IN DRY INTRUSION ON
TUESDAY NIGHT IS SUFFICIENT TO WARRANT DOWNWARD ADJUSTMENT TO CHC
POPS AND INTRODUCTION OF DRIZZLE 00-06Z. CHANGEOVER TO SNOW
PELLETS/IP/FZRA COULD BE RATHER ABBREVIATED BEFORE FZDZ/DZ DEVELOPS.
AS NOTED YESTERDAY, FORECAST HIGHS ARE LIKELY TO OCCUR BENEATH DRY
SLOT, SO MANY LOCATIONS CURRENTLY FORECAST TO SEE LOW/MID 30S MAY
STILL SEE PREDOMINANTLY SNOW.

FOR THE MOST PART THE EXTENDED PERIOD WILL REMAIN QUIET AS HIGH
PRESSURE BUILDS INTO THE GREAT LAKES REGION. HIGH TEMPERATURES ON
WEDNESDAY WILL BRIEFLY TOUCH THE MID 20S BEFORE COLDER AIR FILTERS
IN TO THE REGION. THIS COLDER AIR WILL ALLOW LOW TEMPERATURES TO
DROP BACK INTO THE LOW SINGLE DIGITS FOR BOTH WEDNESDAY NIGHT AND
THURSDAY NIGHT WITH A HIGH ON THURSDAY TO ONLY REACH INTO THE MID
TEENS. TEMPERATURES SLOWLY RISE THROUGH THE END OF THE WEEK AND INTO
THE FIRST PART OF THE WEEKEND. DRY CONDITIONS WILL ALSO PERSIST
THROUGH THE REMAINDER OF THE WEEK AND INTO THE WEEKEND.

MARINE...

A WEAK TO MODERATE SURFACE PRESSURE GRADIENT WILL MAINTAIN WINDS
BELOW 20 KNOTS THROUGH TONIGHT. A COLD FRONT WILL GRAZE THE NORTHERN
PORTIONS OF LAKE HURON MONDAY AND BRING A FRESH NORTHWEST BREEZE
WITH GUSTS TO 30 KNOTS POSSIBLE LATE MORNING AS COLD AND MARGINALLY
UNSTABLE CONDITIONS DEVELOP. HIGH PRESSURE WILL THEN BUILD INTO THE
AREA FROM THE WEST WITH NEARLY CALM CONDITIONS TAKING HOLD MONDAY
NIGHT BEFORE MODERATE SOUTHERLY WINDS EXPAND INTO THE REGION IN
ADVANCE OF THE NEXT STORM SYSTEM DUE INTO THE AREA BY TUESDAY.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

AVIATION.....MR
SHORT TERM...SC
LONG TERM....JVC/RK
MARINE.......JVC


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AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).



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